1. Field of the Invention
This invention pertains to musical instruments, and more particularly to apparatus for adjusting the sound characteristics of string instruments.
2. Description of the Prior Art
Various equipment has been developed to change the tension of the strings in stringed musical instruments. For examples, tremolos, vibratos, or whammy bars for use in electric guitars are well known and in widespread use. The purpose of the tremolos is to change the tension in the guitar strings and thereby change their pitch and other tonal qualities.
Some prior tremolos include a base plate that is fastened to the guitar body. One or more bridges are pivotally connected either to the base plate or to the guitar body. One end of each instrument string is attached, either fixedly or adjustably, to the bridge. The second ends of the strings are attached to tuning pegs on the guitar head. The tension in the strings tends to pivot the bridge in a first direction so as to decrease the string tension. Springs acting on the bridge produce a force that equals or exceeds the string tension to maintain the desired string tension.
There typically are saddles on the bridge in contact with the strings. The saddles are adjustable to vary the string tonal qualities. In addition, there may be a fine tuning device that can vary the tension in each string.
Examples of prior tremolos may be seen in U.S. Pat. Nos. 3,411,394; 4,457,201; 4,632,005; 4,763,555; 4,984,493; 5,109,745; 5,127,298; 5,305,675; 5,373,769; 5,419,227; 5,431,079; 5,435,219; 5,438,902; 5,460,072; 5,477,765; 5,481,955; 5,515,761; 5,520,082; 5,522,297; 5,539,144; 5,551,329; 5,637,818; 5,672,835; 5,708,225; 5,747,713; 5,783,763; 5,808,216; 5,814,746; 5,824,925; 5,847,297; and 5,864,074.
The prior tremolos also include an arm on the bridge. The musician can press on the arm while he is playing the instrument to overcome the spring force and pivot the bridge to reduce the string tension, thereby changing the instrument's sound characteristics. Representative tremolo arms are shown in U.S. Pat. Nos. 5,522,298; 5,637,817; and 5,641,923.
Despite the large variety of prior tremolos presently available, they nevertheless are not completely satisfactory. An undesirable feature of many prior tremolos is that they occupy an excessive volume inside the guitar body. The relatively large amount of material that must be removed from the guitar body both weakens the instrument structurally, and also adversely affects its tonal qualities. That is especially true if material is removed from behind the electronic pickups on electric guitars. U.S. Pat. Nos. 4,984,493; 5,109,745; and 5,477,765 are examples of tremolos that require large cavities in the guitar body.
Another problem with many prior tremolos is that they make restringing and retuning a guitar difficult. That is because the tremolos contain a large number of small tuning-related parts. The tremolos of the U.S. Pat. Nos. 4,632,005; 5,419,227; and 5,477,765 for instance, have movable mounts to which the strings are attached. Obtaining the correct tension of a new string thus requires an interplay of adjustments between the string attachment points on the tremolo and on the tuning pegs on the guitar neck. A related drawback is that manufacturing, assembling, and adjusting the parts is expensive and time consuming. In some prior tremolos, if one string breaks all the remaining strings go out of tune.
Some prior tremolos, such as those shown in U.S. Pat. No. 5,419,227, utilize thumbscrews to adjust the string tension. However, the range of movement of the prior thumbscrews is limited because of the likelihood that the string will twist and slip off the thumbscrew.
A further problem with prior tremolos concerns the pivotal connection of the bridge to the base plate or to the guitar body. Some tremolos, such as those of the U.S. Pat. Nos. 4,632,005; 5,419,227; and 5,477,765 use pins and enclosed holes for the pivoting arrangement. That design renders both assembly and disassembly more difficult than is desired. Another pivot design incorporates a knife edge and post, as are typically shown in the U.S. Pat. Nos. 5,109,745; 5,431,079; and 5,438,902. Although the knife edge design eases the assembly problem compared with the prior pin and fixed hole design, the components required for the knife edge design are undesirably expensive to produce. In addition, the knife edges are prone to wear. A similar connection is shown in U.S. Pat. No. 4,763,555. U.S. Pat. No. 5,435,219 describes flexure plates pivotally connecting the base plate and bridge.
Yet another drawback of many prior tremolos is the design of the springs that counteract the string tensions. It is a desirable feature that the spring force be adjustable, and many prior tremolos incorporate adjustment mechanisms. However, the prior adjustment mechanisms are often complicated and cumbersome to use. U.S. Pat. Nos. 4,984,493, for example, utilizes three gears for the spring adjustment. The adjustment mechanism of the U.S. Pat. No. 5,431,079 requires an external tool for adjusting the spring. In many tremolos, the adjustment mechanism is connected to the guitar body, thus complicating assembly and disassembly.
Thus, a need exists for improvements to tremolos.